July 8, 1918 
Toxoptera graminum in the South 
105 
Tab LB I. —First and last boru generations , date of birth, reproductive period in days, 
daily average and total number of young, total length of life, and maximum and minimum 
temperature during which each generation of Toxoptera graminum lived. Columbia , 
S.C., IQ13-1915 — Continued 
series b— continued 
Generations. 
Repro- 
Young. 
Length 
of life. 
Temperature. 
Eirst 
born. 
Last 
born. 
Dates. 
ductive 
period. 
Daily 
average. 
Total. 
Maxi¬ 
mum. 
Mini¬ 
mum. 
8 
1914. 1914- 
Sept. 5 to Oct. 
19.. 
Days. 
28 
2. OO 
5<5 
Days. 
44 
0 F. 
94 
0 F. 
39 
23 
11 to 
i5-■ 
24 
2. 54 
61 
34 
88 
39 
24 
21 to Nov. 
2.. 
34 
1. 61 
55 
42 
86 
40 
2$ 
30 to Oct. 
10.. 
2 
1. 50 
3 
IO 
85 
57 
26 
Oct. 8 to Nov. 
14.. 
28 
2. 07 
58 
37 
86 
34 
9 
12 to Dec. 
3-- 
42 
.90 
38 
52 
84 
22 
27 
15 to 
14.. 
41 
.76 
3 1 
60 
81 
22 
28 
26 to Nov. 
24.. 
14 
i- 35 
19 
29 
81 
22 
29 
x 9!5 
Nov. 10 to Jan. 
S-- 
24 
.66 
16 
5 6 
70 
21 
IO 
Dec. 1 to Feb. 
4.. 
17 
1.47 
25 
65 
7 1 
21 
30 
2 to Jan. 
13 
0 
. 00 
0 
42 
65 
21 
II 
I 9 I 5* 
Feb. 3 to Apr. 
i3- • 
26 
•73 
19 
69 
83 
27 
SERIES C 
1915. 1915 
1 
Apr. 
10 to May 
17. . 
.2 2 
1.63 
36 
37 
92 
44 
2 
20 to 
18. . 
19 
1. 94 
37 
28. 
92 
54 
3 
28 to 
*3-- 
7 
1. 71 
12 
15 
90 
5 6 
4 
May 
6 to June 
20.. 
25 
2. 20 
55 
45 
95 
56 
2 
11 to 
2.. 
i5 
1. 60 
24 
22 
93 
56 
5 
14 to 
21.. 
23 
2. 04 
47 
38 
95 
56 
6 
21 to 
21.. 
15 
*• 73 
26 
3i 
95 
56 
7 
3 1 to 
3°- • 
*5 
1. 60 
24 
30 
95 
56 
3 
3 1 t0 
26.. 
18 
2.44 
44 
26 
95 
56 
VARIATIONS IN DURATION OF INSTARS AS AFFECTED PRIMARILY BY 
TEMPERATURE CONDITIONS 
Temperature conditions play an important r 61 e in the duration of 
instars in Toxoptera graminum . To ascertain the exact variation in 
length of instars a series of molting experiments was conducted in 1914 
during the months of March, April, May, June, and August. It was 
intended that a series should be conducted every month for one whole 
year, but other pressing work prevented this. Enough data, however, 
have been gathered from the experiments actually carried on to show the 
positive influence of this factor. 
By referring to Table II it will be seen that there was a gradual 
decrease in the length of individual instars from March to August, the 
instars in March having been from two to three times as long as those in 
August. 
